A snapshot function is known as one of the functions of a storage apparatus. According to the snapshot function, an image of a target logical volume at the point in time of a specified snapshot acquisition (a snapshot image) is maintained. That is, even when new data is written to a write-destination area in the target logical volume subsequent to a snapshot acquisition time point, the data in this write-destination area is held without being deleted.
The technology disclosed in Patent Literature 1 is technology related to the snapshot function. In Patent Literature 1, in a case where a certain logical page in a flash memory is used as a write destination for new data, a second physical page into which the new data is to be written is associated anew with the write-destination logical page in addition to a first physical page, which is allocated to the write-destination logical page and is storing the old data. That is, the first physical page in which the old data is stored and the second physical page in which the new data is stored are mapped to the same logical page in the flash memory, and the old data is used as the snapshot.